Roundup of Recent Science Discoveries, 2004

—By Borgna Brunner

Sedna Debuts, Rattling Poor Pluto

Artist's rendition of the planetoid Sedna

On March 15, 2004, astronomers confirmed the discovery of the most distant object ever identified in our solar system. Twice as far from the Sun as any known object, this red mass has an unusually elliptical orbit that takes a staggering 10,500 years to complete. Officially called 2003 VB12, its discoverers claim that it is the first known object from the long-hypothesized Oort Cloud, believed to be home to billions of frozen comets. The object's surface temperature is about minus 400°F (minus 240°C). Its frigid celestial homeland inspired its informal name, Sedna, the Inuit goddess of the icy northern oceans. In addition to its unparalleled coldness and distance, Sedna also distinguishes itself as the largest object identified since Pluto's discovery in 1930. About three-quarters of the size of Pluto, it is considered a planetoid (a minor planet or asteroid). Thought to be composed of rock and ice, it has a reddish hue similar to that of Mars.

In the process of defining Sedna, poor Pluto's fragile standing as a planet has once again come under attack—you may recall that unpleasant business back in 1999 when rumors circulated in the press darkly hinting that Pluto was in danger of a demotion. The International Astronomical Union (IAU) even found it necessary to issue a press release reassuring a distraught public that “no proposal to change the status of Pluto as the ninth planet” was in the works. But while the IAU continues to stand by Pluto, plenty of astronomers would like to wrest it from the company of its eight planetary brethren, pointing out that Pluto has less family resemblance to sublime Saturn than to brassy little Sedna. One of Sedna's discoverers, Mike Brown of the California Institute of Technology, makes a compelling case against Pluto, though coming from a partisan of the new planetoid, it's not nearly as cold-blooded as you might expect:

Either Pluto is not a planet, or many other things are planets. Which is a better choice? I want my planets to be more special, not less special, so I favor Pluto not being a planet. Emotionally, though, I have to admit that I have grown up thinking Pluto is this special odd-ball planet at the edge of the solar system. While I now know scientifically that Pluto is less special, it's still hard to let go.

What with quasars,red giants, and brown dwarfs presumably taking up their time, why are astronomers still arguing about something as fundamental as whether Pluto deserves to be called a planet? Astonishingly, there's no official scientific definition of a planet, beyond a few principles: it must orbit a star and be spherical, and it cannot have been subject to internal nuclear fusion, which would make it a star. Astronomer Gibor Basri of the University of California, Berkeley, admits, “It's something of an embarrassment that we currently have no definition of what a planet is. People like to classify things. We live on a planet; it would be nice to know what that was.”

Back when astronomers first welcomed Pluto into the solar system, it was thought to be the fifth largest planet, 12% larger than our own. Not only has sophisticated astronomical measurement reduced it to ninth place, but given that astronomers have only scratched the surface of the sky—surveying just 15% so far—there are sure to be even bigger, more brazen Sednas in Pluto's future.

Grand Old Galaxy

The Milky Way as photographed by the Hubble Telescope

It's not news among scientists that our galaxy is one of the very oldest in the universe, but until now researchers were unable to determine just how old—estimates ranged from 10.4 billion to 16 billion years. Now astronomers have been able to narrow down their calculations to within 800 million years of the Milky Way's birth. Give or take a few million, the Milky Way has reached the grand old age of 13.6 billion years.

The age of the Milky Way is in part gauged by calculating the age of two of its oldest stars (called A0228 and A2111, part of the globular cluster NGC 6397). Once astronomers determined these stars were 13.4 billion years old, they knew that the Milky Way was at least as old as these galactic inhabitants. But while these are the oldest stars that have been discovered in our galaxy, they are in fact members of a second generation of stars. Were scientists to locate stars from the very first generation, they would have a far more accurate benchmark with which to measure the age of the Milky Way.

How do scientists know that stars A0228 and A2111 are old, but not among the oldest? A first-generation star is made up almost exclusively of hydrogen, and has a relatively short, violent life. When it explodes as a supernova, its death generates the creation of heavier elements. Second-generation stars, such as A0228 and A2111, are built from those heavier elements.

These two second-generation stars actually reveal a lot more than their own age. One of the elements they contain is beryllium. Because beryllium is known to increase over time, it works as a kind of “cosmic clock.” It permits astronomers to calculate the interval of time between when the first generation of stars exploded and synthesized beryllium, and when this second generation of stars containing beryllium was formed. That interval has been measured to be about 200 million years. An international team of astronomers used the European Southern Observatory's Very Large Telescope (VLT), located in Chile, to make these highly complex measurements. “Just a few years ago,” team leader Luca Pasquini remarked, “Any observation like this would have been impossible and just remained an astronomer's dream!”

By adding that interval of 200 million years to the age of the two stars (13.4 billion years), astronomers were able to estimate the age of the first generation of stars in our galaxy—13.6 billion years—and thus at the age of the Milky Way itself. Given that scientists now fix the age of the universe at 13.7 billion years, that makes us the proud denizens of one of the most established and venerable of galaxies.

Gone Fishing

A deep-sea Angler fish

A partial inventory of the latest expedition of the Census of Marine Life (CoML), which in the summer of 2004 ventured into one of the least explored regions of our oceans, revealed 180 species of mid-water fish, 87 near-bottom fish, 5 never-before-seen squid and angler fish, and one astoundingly massive ring of plankton. CoML is a highly ambitious undertaking whose mission is to record the life within our oceans. The billion-dollar project involves more than 300 scientists from 53 countries and will take a decade to complete. Hundreds of thousands of animals and plants are to be inventoried, adding tremendously to the 210,000 marine life forms known to science. Census scientists estimate that perhaps only one-tenth of the life in our oceans is currently accounted for. “We haven't spent enough time exploring our own planet,” says Barbara A. Block, a Johns Hopkins professor involved in the census, “We don't like to tell anyone we're ignorant about the oceans, but we are.”

The most recent expedition of the census was the Norway-led MAR-ECO voyage that explored the Mid-Atlantic Ocean Ridge over two months in the summer of 2004. The 3,728-mile-long Mid-Atlantic Ocean Ridge stretches from Iceland to the Azores, a range of volcanic undersea mountains whose height and length rival anything on dry land. It is one of the least explored areas on the planet. Scientists were surprised to find it so densely populated and diverse. Among the most exotic of their discoveries was an Aphyonus gelatinosus, a fish covered with a pink and blue gelatinous layer; and a deep-sea angler fish, from whose head protrudes something resembling a glowing fishing rod, which is used to lure its prey conveniently close to its mouth. Another unusual find was a tremendously wide ring of plankton that spanned 6.2 miles. And census scientists are still puzzling over one pair of ragged claws scuttling across the floors of silent seas. After discovering a series of mysterious, evenly spaced, 5-cm-wide holes that looked as though some creature had “used a sewing machine to create this landscape,” scientists eventually collared an unlikely culprit—a blind, deep-sea lobster.

A Leg Up on Lucy

An artist's sculpture of the hominid Orrorin

What first separated us from the apes on the evolutionary tree was bipedalism, our ability to walk upright (bigger brains developed much later). The most famous of all early bipeds was of course Lucy,Australopithecus afarensis, estimated to be 3.2 million years old. As Donald Johanson, Lucy's discoverer, puts it, “bipedalism is the most distinctive, apparently earliest, defining characteristic of humans.” Since Lucy's discovery in 1974, however, at least one older human ancestor has been confirmed: Australopithecus anamensis, uncovered in 1995, was on his feet about a million years before Lucy.

In the years since this last discovery, several finds have challenged the age of our earliest ancestors. None, however, has yet found wide acceptance among paleoanthropologists. One of the most dramatic—and blisteringly controversial—was the discovery in 2000 of Orrorin tugenensis, uncovered in Kenya by French paleonanthropologists Brigitte Senut and Martin Pickford. These fossil fragments from five chimp-sized creatures date back an astounding 6 million years. But Orrorin's credentials as a hominid, to put it diplomatically, were sharply called into question by the scientific community. As a London Telegraph article at the time described Orrorin's reception, it “provoked an unseemly outbreak of name-calling, litigation, and academic feuding between some of the world's finest anthropological minds.” While Orrorin is indeed 6 million years old, no definitive proof confirmed that it was anything other than our nearest relative, the chimpanzee.

But powerful evidence that Orrorin walked upright has now been offered by Robert Eckhardt, professor of developmental genetics and evolutionary morphology at Pennsylvania State University. After performing a CT scan on Orrorin’s fossilized thighbone, Eckhard concluded that it contained the properties of a human thighbone rather than those of a chimp or ape. “Now, for the first time, we have solid evidence dated to six million years ago of an intermediate creature between humans and the apes that demonstrated upright posture and bipedalism,” Eckhard maintained, “And the dating of this fossil is unusually secure.” If these assertions gain acceptance in the contentious world of paleoanthropology, then the evolutionary split between apes and hominids occurred at least 2 million years earlier than previously thought—Orrorin, our newest oldest ancestor, would have walked the Earth an amazing 6 million years ago.

Betting on Black Holes

In July 2004, celebrated physicist Stephen Hawking announced that for the past 30 years he had been wrong about black holes. What's more, his error cost him a long-standing bet, obliging him to present a baseball encyclopedia to John Preskill of the California Institute of Technology. On the bright side, Hawking's black hole recantation had a rather exciting side-effect: “I think,” he ventured, “I have solved a major problem in theoretical physics.”

Formed from a collapsed star, a black hole is a “cosmic vacuum cleaner,” whose gravitational pull is so strong that it sucks up everything in its way. In 1976, Hawking theorized that black holes emit random radiation (later named “Hawking radiation”) and lose mass until they eventually evaporate without a trace. All the matter sucked into a black hole, and all “information” about it (its quantum mechanical properties), would then be lost forever.

But Hawking's theory contradicts an essential principle of quantum physics: no information can ever be truly destroyed. Black holes, if Hawking was right, defy the laws of the universe as we know it. This radical theory, according to Preskill, “precipitated a genuine crisis in fundamental physics.” Preskill resisted accepting what became known as the black hole “information paradox,” and in 1997 Hawking (along with another colleague) bet him that “information swallowed by a black hole is forever hidden from the outside universe and can never be revealed, even as the black hole evaporates and completely disappears.”

Seven years later, Hawking claims to have solved the very paradox he created. According to his revised theory, black holes eventually open up, revealing information about what went into them—“the information remains firmly in our universe,” Hawking asserted. Preskill was pleased enough at having won the bet, but acknowledged, “I'll be honest, I didn't understand the talk.” Neither did most others in the audience of the 17th International Conference on General Relativity and Gravitation in Dublin, leaving a stunned group of 800 scientists not sure what had hit them. Hawking's published proof of his revolutionary findings will follow, but in the meantime, he has paid off his bet to Preskill. The bettors had agreed upon an encyclopedia, which, unlike a black hole, is something “from which information can be recovered at will.”

For years, scientists have speculated whether Mars once contained water. The significance of discovering water on Mars of course meant that the planet may have had the potential to support life. But despite many tantalizing findings, no definitive evidence had been uncovered. The landing of two Mars Rovers, Spirit and Opportunity, in Jan. 2004, changed all that. The rovers soon began sending back astonishing images of rippled layers of sediment that scientists confirmed had once formed the bottom of a sea, as well as evidence of mineral deposits that could only have been left behind by water. These and other findings confirmed that not only did Mars once have water, but it had been covered with vast pools of it! The journal Science declared it the scientific breakthrough of the year, and marveled at the odd contraptions that made the Mars discovery possible: “Inanimate, wheeled, one-armed boxes roaming another planet have done something no human has ever managed. They have discovered another place in the universe where life could once have existed.”